The esophagus is a tubular organ that carries food and liquid from the throat to the stomach. The interior surface of the esophagus contains muscles that rhythmatically contract whenever a person swallows. This contraction generally occurs as a sweeping wave carrying food down the esophagus to the stomach. This sweeping wave of contraction is typically referred to as peristalsis. An upper esophageal sphincter (UES) is located at an upper end of the esophagus. The UES is a muscle that serves as a valve between the esophagus and the pharynx from which the esophagus receives food and liquid when swallowing.
The lower esophageal sphincter (LES) is located at a lower end of the esophagus. The LES is a muscle that serves as a valve between the esophagus and the stomach. The LES protects the lower esophagus from stomach acid and bile, which cause the discomfort of heartburn and in time can damage or scar the esophagus.
The diaphragm is a muscular membrane that assists is respiration and intersects the upper Gastrointestinal (GI) tract at an approximate right angle, typically within the length of the LES, creating a pressure inversion point (PIP), which is often referred to as the respiratory inversion point (RIP). As used herein, an “upper GI tract” includes at least the UES, esophagus, LES and at least portions of the pharynx and stomach. The PIP is named as such because it is a point along the length of the upper GI tract (typically within, but sometimes proximate to, the LES) where the muscular pressure in response to respiration inverts. Above the PIP, pressure increases during inhalation and decreases during exhalation. In contrast, below the PIP, the pressure decreases during inhalation and increases during exhalation. A hiatal hernia occurs if the PIP (i.e., the intersection of the diaphragm and the LES) is not within the LES, but is located below the LES within the upper regions of the stomach
Manometry is the recording of muscle pressures within an organ. Esophageal manometry measures the muscular pressure exerted along the upper GI tract, for example, during peristalsis. Esophageal manometry is used to evaluate the contraction function of the upper GI tract in many situations (e.g., breathing, swallowing food, swallowing liquid, drinking, coughing, etc.) and can be useful for diagnosing symptoms that originate in the esophagus, for example, difficulty in swallowing food or liquid, heartburn, and chest pain to determine the cause of the symptoms, for example, dysphasia or echolalia.
A variety of esophageal manometry systems have been used to study pressure along the upper GI tract. Such systems typically include a probe that is inserted into the upper GI tract and one or more pressure sensors that detect pressure from different locations within the upper GI tract. One type of a probe is a catheter. An esophageal manometry system that has a catheter as a probe is a referred to herein as a catheter-based esophageal manometry system. Types of catheter-based esophageal manometry systems include solid state systems and water perfuse systems. In water perfuse systems, pressure sensors are located external to the catheter. Each pressure sensor has a corresponding tube that extends into the catheter and pumps fluid (e.g., water) at some longitudinal location of the catheter against the interior surfaces of the GI tract. The pressure resulting from the impact of the fluid against the interior surface is transmitted via the fluid through the tube to the pressure sensor, where it is detected. In contrast, solid state systems do not use fluids, and each sensing element is attached to or embedded within the catheter and detects pressure locally at the point of impact with the interior surface of the upper GI tract. Each sensor transmits its detected values out of the catheter using an electronic or optical signal.
Existing solid state, catheter-based, esophageal manometry systems typically include only four to eight sensors that detect pressure values during a given temporal interval. Such sensors typically are located several centimeters (i.e., more than three centimeters) apart from one another. Such systems may include an application that displays the detected values as line trace plots to a user. The low spatial resolution of the sensors in such systems results in a low spatial resolution of information being detected and displayed to the user for any given temporal interval. To increase the spatial resolution of detected values in such systems, the catheter may be moved such that the sensors detect values at other locations, for example, locations between the previous locations of the sensors. These latter detected values, however, are detected during different temporal intervals than previous values, so the user still is not provided spatially dense information during a single temporal interval.
Water perfuse catheter-based systems are described in “Topography of the esophageal peristaltic pressure wave,” by R. Clouse, American Journal of Physiology, 1991; 261 (Gastrointest Liver Physio 24): G677-G684, and in “Topographic Imaging of Esophageal Manometric Signals,” R. Clouse, (Motility 1999; 48: 11-13), and have been made available from Medical Measurement Systems, b.v. of Sweden). Water perfuse catheter-based system may include a catheter and up to twenty one tubes where each tube has an opening on its side at a different longitudinal location along the catheter from which it releases water. The resulting pressure from tissue contact at each release site is then transmitted through the water in the tube to a corresponding sensor. Each tube opening is spaced approximately one centimeter apart from a nearest other tube along the longitudinal axis of the catheter. Thus, a water perfuse catheter-based system may have a higher spatial resolution than existing solid state, catheter-based esophageal manometry systems.
An esophageal manometry system may include or be accompanied with an application that visually indicates the values detected by the sensors to a user, and may be capable of visually indicating the values detected by the sensor on a temporal plot in real time using a line trace technique. As used herein, a “temporal plot” is a plot having a temporal axis, where, for each of a plurality of temporal intervals, values detected during the temporal interval are visually indicated at a temporal position relative to the temporal axis that corresponds to the temporal interval. The values detected during different temporal intervals are visually indicated concurrently. A temporal plot is useful to concurrently illustrate values of a physical property detected at one or more locations over time.
As used herein, a value detected for a physical property is visually indicated “in real time” if the duration of time between the time at which the value was detected and the time at which the value is initially visually indicated is short enough relative to the rate at which the physical property changes such that the visually indicated value may be considered the current value of the physical property at the time of its initial visual indication. Such visually indicated value may be considered the current value because, even if the physical property has changed during the time between its detection and its initial visual indication, the rate of change is slow enough such that the amount of change is tolerable in the context in which the value is being used.
Thus, in the context of esophageal manometry, a detected pressure value at a location in the esophagus is visually indicated “in real time” if the duration of time between the time at which the pressure value was detected and the time at which the value is initially visually indicated is short enough relative to the rate at which the pressure changes in the esophagus such that the visually indicated pressure value at the time of its initial visual indication is considered the current value of pressure at the location.
As used herein, a “line tracing technique” of visually indicating values detected at different locations over time on a temporal plot means, for each location, visually indicating a baseline for the location, the baseline running parallel to the temporal axis. The value detected at the location during each temporal interval is represented as an offset from the baseline at a temporal position relative to the temporal axis that corresponds to the temporal interval. The amount of the offset corresponds to the detected value. Each visually indicated value detected at the location is connected by a continuous line, which, depending on the detected values, may be a straight line or a curved line.
Some such software applications also concurrently visually indicate detected values on a temporal plot and a profile plot, but not in real time (i.e., post hoc). As used herein, visually indicating detected values “post hoc” means not visually indicating the detected values in real time. Typically, the detected values are first recorded and then the recorded values are extracted by a program that visually indicates the values on the temporal plot and the profile plot, concurrently. As used herein, a “profile plot” is a plot that has a spatial axis, where, for each of a plurality of temporal intervals, for each value detected. At a different location along a dimension (i.e., a spatial dimension) from a reference point during the temporal interval, the value is visually indicated at a spatial position relative to the spatial axis. The spatial position corresponds to the location at which the value was detected. At any given time, only values detected during a single temporal interval are visually indicated on the profile plot.
The temporal plot on known systems that visually indicate values post hoc may use a line tracing technique or a contour technique. As used herein, displaying values of a physical property detected by sensors located at different locations along a dimension of an organism over time on a temporal plot using a contour technique means the following. For each of a plurality of temporal intervals of the period, for each of a plurality of the sensors, a value of the physical property detected by the sensor during the temporal interval is visually indicated at a coordinate of the temporal plot. The temporal plot has a temporal axis representing time and a spatial axis, oriented orthogonally to the temporal axis, representing the dimension. The value is visually indicated at the coordinate using a tone (i.e., a color or grayscale value) corresponding to the value, and the coordinate has a spatial position relative to the spatial axis that corresponds to the location of the sensor and has a temporal position relative to the temporal axis that corresponds to the temporal interval.
The contour technique employed by known systems for visually indicating detected values on a temporal plot is static in that the positions of the detected values displayed on the temporal plot do not change and the temporal intervals displayed on the temporal plot remain fixed as the user views the temporal plot.
Accordingly, for such a static temporal plot visually indicated post hoc along with a profile plot, even if the profile plot changes with time to display values from different temporal intervals, there is no correlation to the values being visually indicated on the profile plot and the visual indication of detected values on the temporal plot.
Further, in such known systems when values are visually indicated on a temporal plot and a profile plot, concurrently, post hoc, the temporal axis of the temporal plot is oriented vertically on the image presented to the user and the spatial axis of the temporal plot and the profile plot are oriented horizontally on the image presented to the user.
Further, although known esophageal manometry systems visually indicate detected values on a profile plot post hoc, such systems do not visually indicate detected values on a profile plot in real time.